Presently, thanks to progress in technologies, many electronic devices are developed for satisfying people's demands. For providing people with more convenience in lives, electronic devices with increasingly stronger functionality are introduced. In order to enhance functions of electronic devices, ambient light sensors are disposed for sensing the light intensity in the environment and hence executing the corresponding functions such as adjusting the light intensity of the backlight module of an electronic device or telling the user the light intensity in the environment. In addition, ambient light sensors can be disposed in cameras so that the flashlight can be activated automatically once the environmental light intensity is insufficient. Thereby, it is known from the above that the applications of ambient light sensors are becoming wide-spreading.
After an ambient light sensor senses light, it can produce a corresponding light-sensing signal according to the light intensity. The characteristics of the light-sensing signal vary according to different light intensity. For example, the amplitude of the light-sensing signal changes as the light intensity varies. When the light intensity is strong, the amplitude of the light-sensing signal is high. On the contrary, when the light intensity is weak, the amplitude of the light-sensing signal is low. Thereby, the back-stage circuit of an electronic device can know the light intensity according to the characteristics of the light-sensing signal for executing the corresponding functions. Nonetheless, the light-sensing signal output by a modern ambient light sensor cannot be used directly for controlling the back-stage circuit of the electronic device. The electronic device needs to process the light-sensing signal before it can control the back-stage circuit. Consequently, the burden and cost of the electronic device are increased.
Besides, due to material and process factors, the characteristics of different ambient light sensors vary. Even the characteristics of ambient light sensors manufactured using identical materials and processes may not be completely identical. Thereby, while sensing the same light source using different ambient light sensors, the light-sensing signals output by these ambient light sensors differ, which causes an electronic device unable to know the light intensity of the light source with accuracy and hence unable to execute the corresponding functions accurately. Even worse, erroneous functions might be executed instead. For instance, a camera might activate its flashlight even under sufficient light. Based on the above description, it is known that modern electronic devices are influenced by the not-completely-identical characteristics of their ambient light sensors, which may lead to deterioration of their performance.
Accordingly, the present invention provides an ambient light sensing module for solving the problem described above. The present invention can produce a pulse-width modulation (PWM) signal related to the light intensity as the control signal of an electronic device for improving the drawbacks according to the prior art. In addition, the characteristics of the ambient light sensing module according to the present invention can be trimmed and thus enhancing the accuracy of the ambient light sensing module.